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<div class='page-title'>Actions</div>

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<br>The Command pattern is described in <i>Design Patterns</i>, where menu
items are used as an example implementation.
<p>In Swing, the <tt><a href="http://java.sun.com/javase/6/docs/api/javax/swing/Action.html">Action</a></tt>
interface and the <tt><a href="http://java.sun.com/javase/6/docs/api/javax/swing/AbstractAction.html">AbstractAction</a></tt>
base class implement the Command pattern. They eliminate duplication of
code, and separate tasks from the details of their invocation :
<ul>
<li>
the same <tt>Action</tt> object can be invoked in multiple ways, usually
through a <tt>JMenuItem</tt> and <tt>JToolBar</tt> button (<tt>JButton</tt>
and <tt>JTextField</tt> can also be used)</li>

<li>
text, mnemonic, accelerator, tooltip, command <tt>String</tt>, and icon
are all defined once in an implementation of <tt>Action</tt>, and are all
shared by all associated graphical elements</li>

<li>
the enabled/disabled state of an <tt>Action</tt> is always reflected by
all associated graphical elements</li>

<li>
<tt>Action</tt> objects can be passed directly to the constructor of <tt><a href="http://java.sun.com/javase/6/docs/api/javax/swing/JMenuItem.html#JMenuItem(javax.swing.Action)">JMenuItem</a></tt>
and <tt><a href="http://java.sun.com/javase/6/docs/api/javax/swing/JButton.html#JButton(javax.swing.Action)">JButton</a></tt>,
and also to <tt><a href="http://java.sun.com/javase/6/docs/api/javax/swing/JToolBar.html#add(javax.swing.Action)">JToolBar.add</a></tt></li>
</ul>
<b>Example</b>
<p>A <tt>JMenuItem</tt> corresponding to <tt>File -> Save</tt> can be created
using this <tt>Action</tt> :
<br>
<PRE>

<span class='keyword'>package</span> hirondelle.stocks.file;

<span class='keyword'>import</span> java.awt.event.*;
<span class='keyword'>import</span> javax.swing.*;
<span class='keyword'>import</span> java.util.*;
<span class='keyword'>import</span> hirondelle.stocks.portfolio.PortfolioDAO;
<span class='keyword'>import</span> hirondelle.stocks.portfolio.CurrentPortfolio;
<span class='keyword'>import</span> hirondelle.stocks.util.ui.UiUtil;
<span class='keyword'>import</span> java.util.logging.Logger;
<span class='keyword'>import</span> hirondelle.stocks.util.Util;

<span class='comment'>/**
* Save the edits performed on the {@link CurrentPortfolio}, and update the display 
* to show that the &lt;tt&gt;CurrentPortfolio&lt;/tt&gt; no longer needs a save.
*/</span>
<span class='keyword'>public</span> <span class='keyword'>final</span> <span class='keyword'>class</span> FileSaveAction <span class='keyword'>extends</span> AbstractAction <span class='keyword'>implements</span> Observer {

  <span class='comment'>/**
  * Constructor.
  *  
  * @param aCurrentPortfolio is to be saved by this action.
  */</span>
  <span class='keyword'>public</span> FileSaveAction(CurrentPortfolio aCurrentPortfolio) {
    <span class='keyword'>super</span>(<span class='literal'>"Save"</span>, UiUtil.getImageIcon(<span class='literal'>"/toolbarButtonGraphics/general/Save"</span>)); 
    fCurrentPortfolio = aCurrentPortfolio;
    fCurrentPortfolio.addObserver( <span class='keyword'>this</span> );
    putValue(SHORT_DESCRIPTION, <span class='literal'>"Save edits to the current portfolio"</span>);
    putValue(
      ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_S, ActionEvent.CTRL_MASK)
    );
    putValue(LONG_DESCRIPTION, <span class='literal'>"Save edits to the current portfolio"</span>);
    putValue(MNEMONIC_KEY, <span class='keyword'>new</span> Integer(KeyEvent.VK_S) );    
  }

  <span class='keyword'>public</span> <span class='keyword'>void</span> actionPerformed(ActionEvent e) {
    fLogger.info(<span class='literal'>"Saving edits to the current portfolio."</span>);
    PortfolioDAO portfolioDAO = <span class='keyword'>new</span> PortfolioDAO();
    portfolioDAO.save( fCurrentPortfolio.getPortfolio() );
    fCurrentPortfolio.setNeedsSave(<span class='keyword'>false</span>);
    fCurrentPortfolio.notifyObservers();
  }  
  
  <span class='comment'>/**
  * Synchronize the state of this object with the state of the 
  * &lt;tt&gt;CurrentPortfolio&lt;/tt&gt; passed to the constructor.
  *
  * This action is enabled only when the &lt;tt&gt;CurrentPortfolio&lt;/tt&gt; is titled and 
  * needs a save.
  */</span>
  <span class='keyword'>public</span> <span class='keyword'>void</span> update(Observable aPublisher, Object aData) {
    setEnabled( fCurrentPortfolio.getNeedsSave() &amp;&amp; !fCurrentPortfolio.isUntitled() );
  } 
  
  <span class='comment'>// PRIVATE //
</span>  <span class='keyword'>private</span> CurrentPortfolio fCurrentPortfolio;
  <span class='keyword'>private</span> <span class='keyword'>static</span> <span class='keyword'>final</span> Logger fLogger = Util.getLogger(FileSaveAction.<span class='keyword'>class</span>);
}
 
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